Webasto Air Top Evo 5500 B User manual

Air Heater
Air Top Evo 3900/5500 B (Gasoline)
Air Top Evo 3900/5500 D (Diesel)
Installation Manual
WARNING!
– Improper installation or repair of Webasto heating and cooling systems can cause fire
or the leakage of deadly carbon monoxide leading to serious injury or death.
– Installation and repair of Webasto heating and cooling systems requires special
Webasto training, technical information, special tools and special equipment.
– NEVER attempt to install or repair a Webasto heating or cooling system unless you
have successfully completed the factory training course and have the technical skills,
technical information, tools and equipment required to properly complete the
necessary procedures.
– ALWAYS carefully follow Webasto installation and repair instructions and heed all
WARNINGS.
– Webasto rejects any liability for problems and damage caused by the system being
installed by untrained personnel.
– Improper installation or installation by untrained personnel voids all warranties on
this product.

Air Top Evo 3900/5500 Table of Contents
www.webasto.us 3 Webasto Thermo & Comfort N.A., Inc.
Contents Page
1. Safety and General Information 5
1.1 Warning Symbols in this Installation Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Regulation for Installation in the Vehicle 6
2.1 Legal Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Position of the Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Fuel Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4 Exhaust System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.5 Combustion Air Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.6 Hot Air Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.7 Hot Air Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.8 Automatic Control of the Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Purpose of the Air Heater 8
4. Installation 9
4.1 Recommended Installation and Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.2 Air Top EVO 3900/5500 Installation Situation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3 Installation Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4 To Install the Heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.5 Optional Mounting Plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.6 Factory Plate / Label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.7 Installation Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5. Hot Air System 13
5.1 External Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6. Fuel Supply 15
6.1 Vehicles with a Carburetor Equipped Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2 Vehicles with Fuel Injection Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3 Vehicles with Diesel Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.4 Fuel Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.5 Fuel Metering Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.6 Fuel Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
7. Combustion Air Supply 19
8. Exhaust Pipe 20
9. Combustion Air Inlet and Exhaust Lines 21
10.Electrical Connections 22
10.1 Heater Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
10.2 Supply Voltage Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
10.3 Control Element (Rheostat) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
10.4 Control Element (SmarTemp) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
10.5 Control Element (MC04/05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
11.Circuit Diagrams 27
11.1 Legend for Circuit Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
12.Starting the Heater for the First Time 32
12.1 Control Element Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
13.Fault Lock-out 34
13.1 Error Code Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table of Contents Air Top Evo 3900/5500
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14.Technical Data 35
14.1 Electrical Components: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
14.2 Fuel for Air Top EVO 3900/5500 B (Gasoline): . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
14.3 Fuel for Air Top EVO 3900/5500 D (Diesel/Heating Oil): . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
15.Version 36
16.Drilling Template 37

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Air Top Evo 3900/5500 Safety and General Information
1. Safety and General Information
1.1 Warning Symbols in this Installation Manual
The purpose of safety symbols is to attract your attention to possible hazardous conditions. This manual uses a series
of symbols and signal words which are intended to convey the level of importance of the safety messages. The
progression of
symbols is described below. Remember that safety messages by themselves do not eliminate danger and are not a
substitute for proper accident prevention measures.
Indicates an imminently hazardous situation which, if not avoided,
WILL result in death or serious injury.
Indicates a potentially hazardous situation which, if not avoided,
COULD result in death or serious injury.
Indicates a potentially hazardous situation which, if not avoided,
MAY result in minor or moderate injury or property damage.
It may also be used to alert against unsafe practices.
These symbols are used to alert the installer to important or useful information
about proper installation of the equipment.
1.2 General Information
Webasto Product North America, Inc. is pleased to provide this installation manual with the AT 3900/5500 air heater.
When installed according to the guidelines stated in this manual, you can expect your customer to enjoy many years of
trouble-free heater operation.
This manual represents our latest effort to produce the best technical documentation possible.
In our efforts towards continuous, ongoing product improvement, we encourage our customers to write to us with
their comments or criticisms concerning this manual and the AT 3900/5500 air heating system.
Please write to us at:
Webasto Product North America, Inc.
Technical Documentation Group
15083 North Road
Fenton, MI 48430
You are also invited to fill out our online questionnaire concerning our technical documentation and web site at:
www.techwebasto.com
If you have any immediate questions concerning this manual, the installation procedures within or the product itself,
please call us at:
[phone]or send a fax to:[phone]
DANGER
WARNING
CAUTION
OR

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Regulation for Installation in the Vehicle Air Top Evo 3900/5500
2. Regulation for Installation in the Vehicle
Read this installation manual in its entirety before installing this equipment.
2.1 Legal Provisions
2.1.1 The installation and service of Webasto heaters requires special expertise and training. Installations
and servicing of Webasto products by untrained, unauthorized personnel and end-users voids all
warranties and releases Webasto Product North America, Inc. and Webasto authorized distributors, dealers
and their personnel from responsibility for damage to Webasto products, any resulting collateral property
damage and personal injury.
2.1.2 Any use, operation, installation, modification or application of the product not described in Webasto manuals,
or subjecting the product to extreme or unusual conditions beyond the limits of specified performance characteristics is
misuse of the product. Failure to comply with all installation instructions is a misuse of Webasto products. The same
applies for repairs without using genuine Webasto service parts. This will void the heaters “official Marks of
Conformity.”
IMPORTANT!
All relevant state and provincial licensing regulations if any, governing the installation and use of auxiliary
heating devices must be observed!
2.2 Position of the Heater
2.2.1 Parts of the vehicle body and other components in the immediate vicinity of the heater must be protected
against excessive heat and the danger of contamination by fuel or oil.
2.2.2 The internal combustion heater must not pose a fire hazard even when overheated. This requirement is
deemed to have been met if care is taken during installation to ensure an adequate distance from all parts, as well as
adequate ventilation and if fire-resistant materials or heat shields are used.
2.2.3 The model/ Serial plate or a duplicate there of (duplicate model/ Serial plate) must be fitted in such a way that
it is still clearly legible when the heater has been installed in the vehicle.
2.2.4 When positioning the heater, all reasonable precautions must be taken to minimize the risk of personal injury
or damage to items in the vehicle.
2.2.5 A clearly visible indicator within the user's field of vision must show when the heater is switched on or off.
2.3 Fuel Supply
2.3.1 Fuel lines are to be installed in such a way that they remain unaffected by torsional stresses created by vehicle
and engine movement.
2.3.2 Fuel lines must be securely fastened to the vehicle every 12 inches (30 cm) or less along the total length from
heater to fuel tank.
2.3.3 Fuel-carrying components must be protected against excessive heat and are to be installed so that any
drippings or evaporating fuel can neither accumulate nor be ignited by hot components or electrical equipment.
2.3.4 In buses, fuel lines are not to be located in the passenger area or in the driver’s compartment. Fuel supply must
not be by means of gravity or pressurization of the fuel tank.
2.3.5 The fuel tank must be equipped with a vent cap or ventilated in another way (vent line).
2.3.6 When a separate fuel supply is used the fuel filler neck must not be located in the passenger compartment and
must have a tightly fitting cap to prevent any fuel leaks.

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Air Top Evo 3900/5500 Regulation for Installation in the Vehicle
2.3.7 The type of fuel and the fuel filler neck must be clearly identified for liquid fuel heaters which have a fuel
supply separate from the vehicle fuel supply.
2.3.8 A label must be affixed to the fuel filler neck warning that the heater must be switched off before refuelling.
An identical warning must also be included in the manufacturer's operating instructions.
2.4 Exhaust System
2.4.1 The exhaust outlet must be positioned in such a way that exhaust fumes cannot get into the interior of the
vehicle through ventilation devices, hot-air inlets or open windows. Also note that exhaust should always point away
from the direction of travel.
2.4.2 Do not route exhaust components within 100 mm (4 inches) of flammable materials such as fuel system
components, polyurethane or similar foam insulation, styene sheet installation, wood and paper products, carpet,
glycol reservoirs, coolant lines, brake lines, electrical wiring, etc.
2.5 Combustion Air Inlet
2.5.1 The air for the combustion chamber of the heater must not be extracted from the passenger cabin of the
vehicle.
2.5.2 The air inlet must be positioned in such a way that it cannot be obstructed by other objects.
2.6 Hot Air Inlet
2.6.1 The supply of heating air must consist of either fresh air or recirculated air and must be taken from a clean area
which cannot be contaminated by exhaust fumes from the engine, the internal combustion heater or any other source
in the vehicle.
2.6.2 The inlet line must be protected by a grating or other suitable means.
2.7 Hot Air Outlet
2.7.1 Hot air lines within the vehicle must be positioned or protected in such a way as to exclude all risk of injury or
damage caused by direct contact.
2.7.2 The air outlet must be positioned or protected so that it cannot be obstructed by other objects.
2.8 Automatic Control of the Heating System
When the engine stops, the heating system must cut out automatically and the fuel supply must be stopped within 5
seconds.
The heating system may remain in operation if a manual unit has already been activated.

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Purpose of the Air Heater Air Top Evo 3900/5500
3. Purpose of the Air Heater
The Webasto Air Top EVO 3900/5500 air heaters are designed
– to heat cabins, boats (Diesel Only), trucks, minibuses, vans and motor homes
– to defrost vehicle windows
– to heat cargo
The air heaters operate independently of the engine and are connected to the fuel tank and the electrical system of the
vehicle.
They may be used for vehicles with either water or air-cooled engines.
They are not designed for heating hazardous substances.

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Air Top Evo 3900/5500 Installation
4. Installation
IMPORTANT!
The regulations governing installation on pages 4 and 5 must be adhered to.
The heater must not be operated without the control unit cover (#9 below) (this will cause the heater to
overheat).
4.1 Recommended Installation and Service Tools
• Digital Multi-Meter - Should be a good quality VAO meter.
• 1/2 Heavy-Duty, low speed drill with good quality, sharp drill bits and a selection of hole saws.
• Mounting/ Drilling Templates.
4.2 Air Top EVO 3900/5500 Installation Situation
NOTE:
Check the installation situation of the relevant vehicle type.
4.3 Installation Location
The heater may be fitted both in the interior or on the exterior of the vehicle.
If it is installed on the exterior ensure that the heater is fitted in a position where it is protected from splashing water
and spray.
The heater must be installed in such a way that no water can ingress into it if the vehicle travels through a water hazard
for which that vehicle is licensed.
The openings for the combustion air inlet port, the exhaust outlet port and the fuel line must be sealed if the heater is
installed in the interior. The seal designed and supplied for this purpose must be used (see Figure 4). The same applies
when using the optional mounting plate and closed cell foam gasket (see Figure 5).
Figure 1. Dimensions of the Heater
9
1
25 24
ØØ
4
151
45
6
423 80
47.5
200
162
8
148
25
3
5
2
7
1. Hot air inlet
2. Hot air outlet
3. Combustion air inlet
4. Exhaust gas outlet
5. Fuel intake
6. Space required for hot air inlet
7. Space required for hot air outlet
8. Space required for removing the heater (service)
9. Cable outlet/Control unit cover (either right or
left)

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Installation Air Top Evo 3900/5500
4.4 To Install the Heater
The M6 nuts used to install the heater must be tightened with a torque of 6 Nm ±1 Nm (4.4 lb.-ft ±74 lb.-ft).
The installation dimensions and space requirement for service access are shown in the installation drawing (Figure 1).
The specified horizontal and axial angles must not be exceeded (Figure 2).
Figure 2. Recommended Installation Positions for AT 3900/5500 Heaters
A seal (Figure 4) must be fitted between the heater and the vehicle body. This seal must be replaced each time the
heater is installed. The support area for the heater foot must be flat. A special tools can be purchased from Webasto to
drill the holes and, if necessary, smooth the support area. The seal can compensate for unevenness of max. 1 mm.
The seal or foam gasket or both must be replaced each time the heater is removed and re-
installed.
Figure 3. Hole Pattern
Figure 4. Seal
Gasoline Heaters
Diesel Heaters
0 - 90°
0 - 90°
0 - 90°
0 - 90°
0 - 90°
0 - 30°
WARNING
Ø7.5
Ø7.5
Ø7.5
Ø26
Ø26
18
12
44
55

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Air Top Evo 3900/5500 Installation
4.5 Optional Mounting Plate
Figure 5. Mounting with optional mounting plate
When using the optional mounting plate and closed cell foam gasket, do not over tighten
the mounting bolts. Doing so will cause the mounting plate to warp and result in stress
damage to the heater and fan motor.
IMPORTANT!
After installation, check that the heater casing is not in contact with any parts of the vehicle body.
A failure to do this may result in the hot air fan binding internally (Figure 6).
Figure 6. Installation
4.6 Factory Plate / Label
The model/serial number plate of the heater must be positioned so that it cannot be damaged and must be clearly
legible when the heater is installed (otherwise a duplicate model plate must be used).
Inapplicable years must be erased from the model plate.
1
2
3
1. Seal - Heater to vehicle floor or optional
mounting plate.
2. Mounting plate - Facilitates installation on
corrugated vehicle floors.
3. Closed Cell Foam Gasket - Seals area
between mounting plate and vehicle floor.
The seal or foam gasket or
both must be replaced
each time the heater is
removed and re-installed.
A mounting plate template is provided in the
installation kit for locating the heater on the floor
of the vehicle. All recommended hole locations
and sizes are included.
WARNING
CAUTION
Ensure that all moving part can move freely

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Installation Air Top Evo 3900/5500
4.7 Installation Example
Figure 7. Installation example with heater in stalled under-bunk. (Recirculation mode)
1
2
345
6
7
1 Control Element (Rheostat) 2 AT 3900/5500 EVO Heater 3 Fuel Metering Pump 4 Fuel Filter (Optional) 5 Fuel Satndpipe 6 Exhaust Muffler (Optional) 7 Fuse Block

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Air Top Evo 3900/5500 Hot Air System
5. Hot Air System
NOTE:
The heater must not be integrated into the vehicle’s air system.
Both recirculation and fresh air modes are possible.
For fresh air mode it must be ensured that the inlet (hot) air is taken from an area protected from splashing water and
spray and in such a way that no water can ingress into the heater if the vehicle travels through a water hazard for
which that vehicle is licensed.
NOTE:
For fresh air mode, an external temperature sensor must be fitted in the appropriate zone. The standard pause speed
for the blower motor is 0 rpm if the external temperature sensor is used
Inside the control unit there is a temperature sensor, which operates the heater in the appropriate heat output range in
conjunction with the control element depending on the intake temperatures and the position of the set point
generator. The heat output is controlled such that after the selected interior temperature has been reached quickly, it is
then kept at this selected value.
The internal diameter of the main section of the hot air line should be:
90 mm (3.54 in.) minimum for the Air Top EVO 5500
80 mm (3.14 in.) minimum for the Air Top EVO 3900
NOTE:
Only materials that can permanently withstand temperatures of at least 130°C (266°F) may be used for the hot air line.
The hot air opening is to be positioned in such a way that the air is not blown on to any parts that cannot withstand
the heat.
IMPORTANT!
In vehicles used to transport people, the air outlet opening is to be directed in such a way that it is
at least 20 cm (8 in.) away from all body parts.
Maximum pressure drop between the inlet and outlet side of the hot air line:
Air Top EVO 3900 2.0 hPa
Air Top EVO 5500 3.0 hPa
1 hPa corresponds to 1 mbar corresponds to 10 mm Water Column (0.4 inches Water Column).
The heaters check the internal temperature rise automatically each time they are switched on. If this is above the
specified limits (150°C / 302°F), the start is cancelled and error messages F10 (Overheat code) is displayed. To ensure
that the heater functions stably, the flow resistance of the connected hot air system must be reduced.
The hot air hose must be secured at its connection points.
If the heater is used in recirculation mode, for example, in the under bunk compartment of a truck’s sleeper, without a
hot air directional outlet grille, do not short circuit the hot air flow.
Figure 8. Hot air inlet and hot air outlet (recirculation mode)

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Hot Air System Air Top Evo 3900/5500
IMPORTANT!
If you use the heater without a hot air inlet hose, the inlet grille supplied with the heater must be
used at all times.
NOTE:
The installation must be checked for:
– Air short circuit between the vehicle’s heating system and the heater air inlet.
– Air short circuit between the heater’s air inlet and the heater’s air outlet (Figure 8).
Figure 9. Hot air inlet with inlet grille
If you use an installation box the air vent must be sealed in such a way that no hot air can get into the installation box.
5.1 External Temperature Sensor
The installation of an external temperature sensor is recommended if the heater is operated in fresh air mode.
5.1.1 To Install the External Temperature Sensor
The external temperature sensor must be installed at medium height in the passenger cabin on vertical surfaces if
possible in the area that requires heating.
The temperature sensor must not
– be in the direct current of hot air (from the vehicle’s own heating system or the hot air heater).
– by close to heat sources (for example the vehicle’s own heating system).
– be placed in direct sunlight (for example on the dashboard).
– be installed behind curtains or the like.
Figure 10. External temperature sensor - optional
External temperature sensor
Cover

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Air Top Evo 3900/5500 Fuel Supply
6. Fuel Supply
The fuel is taken from the vehicle fuel tank or from a
separate fuel tank. The values for the maximum pressure at
the fuel extraction point are shown in Figure 11.
A sign must be affixed to the fuel tank’s filler neck warning
that the heater must be switched off before refuelling.
6.1 Vehicles with a Carburetor Equipped Engine
The fuel may only be extracted using the special Webasto fuel extractor (see Figure 12) as close to the tank as possible.
The connection may be made in either the supply or return line, in which case the return line must lead almost to the
base of the tank (see Figure 13).
The fuel extractor must be fitted in such a way that any air or gas bubbles are automatically discharged towards the
tank (see Figure 12).
Figure 12. Webasto fuel extractor
The fuel extractor should not be located near the engine, as gas bubbles may form in the lines on account of heat
radiated from the engine. This may cause problems during combustion.
Permissible fuel inflow height H At max. pressure in fuel line
0.00 m (0.00 in.) 0.2 bar (2.9 PSI)
1.00 m (39.4 in.) 0.11 bar (1.6 PSI)
2.00 m (78.7 in.) 0.03 bar (0.44 PSI)
Maximum fuel intake height S At max. negative pressure in the
fuel tank
0.00 m (0.00 in.) -0.10 bar (-1.45 PSI)
0.50 m (19.7 in.) -0.06 bar (-0.87 PSI)
1.00 m (39.4 in.) -0.02 bar (-0.29 PSI)
iØ2mm
iØ2mm
iØ2mm
iØ2mm
I2
I2
I1
I1
max.3m
H
S
I2
I1+10 m
1.2 m
8.8 m
I1
I2
Figure 11. Fuel supply
a= 6Ø
8Ø
10Ø
12Ø
0-60°
Ø5
0-60° 0-60°
0-60° 0-60°
0-60°
From Tank
To Engine
To Fuel Metering Pump

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Fuel Supply Air Top Evo 3900/5500
6.2 Vehicles with Fuel Injection Engines
When installing the heater in a vehicle with fuel injection system, it is important to establish whether the fuel pump is
located inside or outside the tank.
If the fuel pump is located inside the tank, fuel can only be extracted from the return line using the Webasto fuel
extractor (see Figure 12), in which case it must be ensured that the return line continues almost to the bottom of the
tank (see Figure 13 for details of the minimum distance from the bottom of the tank). If this is not the case Webasto
fuel extractors or standpipes (see Figures 13, 14 and 15) may be used.
If the fuel pump is installed outside the tank, the fuel connection may also be made between the tank and the fuel
pump, again using only the Webasto fuel extractor (see Figure 12).
6.3 Vehicles with Diesel Engines
The fuel must be taken from the vehicle fuel tank or from a separate tank (see Figs. 13, 14 and 15). This separate fuel
pickup precludes any effect of pressure.
Figure 13. Webasto fuel standpipe
NOTE:
The tank fitting must be made from metal!
6.4 Fuel Lines
Only steel, copper and plastic lines of plasticized, light and temperature-stabilized PA 11 or PA 12 (e.g. Mecanyl RWTL)
pursuant to DIN 73378 may be used for the fuel lines.
Since the lines normally cannot be routed with a constant rising gradient, the internal diameter must not be allowed to
exceed a certain size. Air or gas bubbles will accumulate in lines with an internal diameter of more than 2 mm and
these will cause malfunctions whilst the heater is operating if the lines sag or are routed downwards. The diameters
specified in Figure 11 will ensure that bubbles do not form.
The lines should not be routed downwards from the metering pump to the heater.
Unsupported fuel lines must be secured to prevent them from sagging. They must be installed in such a way that they
cannot be damaged by flying road debris and high temperatures (exhaust line).
The fuel lines must be secure at the connections using hose clamps to prevent their slipping.
*
25
Minimum distance 25 mm (1 in.)
Only use this Standpipe on fuel
tanks constructed from metal
Hole pattern

www.webasto.us 17 Webasto Thermo & Comfort N.A., Inc.
Air Top Evo 3900/5500 Fuel Supply
6.4.1 Connecting Two Fuel Lines with a Coupler Hose
The correct procedure for connecting fuel lines with hosing is shown in Figure 16. Ensure that there are no leaks.
Figure 16. Fuel line / coupler hose connection
6.5 Fuel Metering Pump
The fuel metering pump is a combined delivery,
metering and shut-off system and is subject to
certain installation criteria (see Figures 11 and
18).
6.5.1 Installation Location
It is advisable to install the metering pump in a
cool place. The maximum ambient temperature
must not exceed +20 °C (68 °F) for gasoline
heaters at any time during operation.
The metering pump and fuel lines must not be
installed within range of the radiated heat from
hot vehicle parts. A heat shield must be used if
necessary
.
Plastic tank
Sealing ring
Sealing ring
Tank F i t t i n g
Tank Connector
Figure 14. Fuel supply from plastic tank drain screw
Figure 15. Fuel supply from plastic tank fitting
Clamp
Bubble Bubble
Wrong
Correct
e 17. Fuel Metering Pump DP 2
Air Top EVO 3900/5500 12 and 24 Volt - Diesel
Figure 18. Fuel metering pump DP 30.2 / 30.3
Preferably
15° - 90°
Air Top EVO 3900/5500 12 Volt - Gasoline

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Fuel Supply Air Top Evo 3900/5500
6.5.2 Installation and Attachment
The metering pump must be secured with a vibration-damping mounting. Its installation position is limited as shown in
Figure 18 in order to ensure effective automatic bleeding.
As a result of the risk of corrosion, only genuine Webasto parts may be used for the plug connections between the
metering pump and the metering pump wiring harness.
6.6 Fuel Filter
Only a Webasto filter is allowed to be used if the fuel is expected to be contaminated. Install vertically if possible,
however at least horizontally (check flow direction).
IMPORTANT!
Do not substitute the Webasto supplied fuel filter with a non Webasto replacement. Irregular
heater operation may result.
Figure 19. Fuel filter
A
Ø 5
0° - 90°

www.webasto.us 19 Webasto Thermo & Comfort N.A., Inc.
Air Top Evo 3900/5500 Combustion Air Supply
7. Combustion Air Supply
Under no circumstances may the combustion air be taken from areas occupied by people. The combustion air intake
opening must not point in the direction of travel. It must be located so that it cannot become clogged with dirt and
road debris.
NOTE:
An intake silencer must be fitted if the intake hose length is shorter than 0.6 m.
NOTE:
The combustion air must be extracted using a combustion air line from a position that is as cool as possible and
protected from splashing water.
Do not use an exhaust line as the combustion air line since otherwise the metering pump cable from the combustion
air inlet port may be damaged.
The combustion air opening must not be under the minimum water drive-through level permitted for the vehicle.
See the regulations for the installation for further regulations.

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Exhaust Pipe Air Top Evo 3900/5500
8. Exhaust Pipe
Rigid pipes of unalloyed or alloyed steel with a minimum wall thickness of 1.0 mm (3/64 in.) or flexible piping of alloyed
steel only must be used as exhaust line.
The exhaust pipe is secured to the heater using a clamping collar, for example. See the ‘regulations for installation’ for
other requirements.
The exhaust muffler should ideally be installed near the heater.
The heater may also be operated without a muffler.
Figure 20. Exhaust muffler - exhaust flow is non-directional (arbitrary)
Ø 6.5
0-90° 0-90°